1. Field of the Invention
The present invention relates to a substrate type dipole antenna, and, more particularly, to an ultra-band substrate type dipole antenna which blocks leakage current on an outer part of an external conductor of a coaxial cable and therefore prevents distortion of a radiation pattern.
2. Description of the Related Art
With the industrialization of Ultra WideBand (UWB) wireless communication technologies, various UWB wireless communication technologies are expected to be applied to personal computers, electronic appliances, and personal wireless terminals, etc. Accordingly, an antenna technology, which can provide a low price unit, compact size and maximum electric performance, is also required. Generally, a substrate type antenna by a printed circuit board technique is a representative example of a reasonable-price antenna for use in a ultra wideband. A variety of dipole antennas are fabricated in the category of the substrate type antennas, as exemplarily disclosed in U.S. Pat. No. 6,642,903.
FIG. 1 is provided for explanation of one example of electric current feed to a substrate type antenna. An antenna 10 is connected with a coaxial cable 30 to transmit and receive electric waves. Referring to FIG. 1, feed is performed with respect to the antenna through the coaxial cable 30 which is connected to the lower part of the connector 20.
Generally, in designing substrate type antennas, a metal pattern is used in the substrate so that high frequency electric current can flow. Additionally, an antenna is designed to have maximum radiation in the vertical direction with respect to the substrate plane and also in the left and right direction of the antenna. Meanwhile, the radiation pattern of an antenna is influenced by the electric current flowing there through. Therefore, a leakage of electric current may occur on an outer part of an external conductor of the coaxial cable 30 when the coaxial cable 30 is connected to the antenna. Due to such leakage of electric current, the radiation pattern of the antenna changes, and therefore, the maximum radiation that the designer originally anticipated is not obtained.
FIG. 2 shows the change of radiation pattern based on the antenna, when the feed method of FIG. 1 is employed. Referring to FIG. 2, the maximum radiation is deviated to the coaxial cable 30 due to partial leakage of electric current toward the outer part of the external conductor of the coaxial cable 30 when the electric current is fed to the antenna.
In order to reduce the above-mentioned problems, a feed method as shown in FIG. 3 has been conventionally suggested. Another example of electricity feed to the substrate type antenna will be briefly described below with reference to FIG. 3.
As shown in FIG. 3, an antenna with a 90° bent coaxial cable has a leakage of electric current in the direction of the coaxial cable, and therefore, the problem of having a shift of the maximum radiation of the antenna from the vertical direction of the antenna surface to the connector can be somewhat reduced. However, this type of electric feed has an interference of electric waves between the antenna and the coaxial cable due to the perpendicular orientation of the coaxial cable with respect to the antenna substrate. Therefore, the radiation pattern of the antenna varies from the uniform pattern.